Folding apparatus to fold paper which has been printed on is described for example, in German Patent No. 25 12 368, in which folded products are collected on a collection or assembly cylinder, to be transferred to a transfer cylinder for subsequent transfer to a belt system. The belt system then transports the folded, and collected sheets to a second longitudinal folding apparatus. A perforating groove ring is integrated with the transfer cylinder. A perforating blade cylinder, having one or more perforating blades with projecting pins or teeth, is operatively associated with the transfer cylinder. The toothed perforating blade, in combination with the perforating groove on the transfer cylinder, forms perforations on all the assembled, superimposed folded products at the level of the second longitudinal fold, in order to provide for a temporary association of the respective products, so that they are connected or fixed together and prevented from sliding or slipping with respect to each other. The perforation is carried out when the folded products are bent or curved, since they are located on the transfer cylinder. The folded products, after transfer to the belt system, are then stretched and the change in orientation of the folded products, from the bent position on the cylinder to a flat position on the transport system, at times loosens the interengagement of the sheets due to the perforation. To prevent such loosening, the radius of the perforating groove ring, as well as the transfer cylinder, must be large.
The perforating apparatus, the collection cylinder and the transfer cylinder are usually retained in a frame portion of the machine. The longitudinal folding apparatus is a separate unit, located in a second separate machine frame. The position of the second longitudinal fold should occur at the center of the folded products. To align the position of the second fold with the perforations, which are also to be at the center, requires adjustment of the position of the second longitudinal fold independently of any position of the perforating blade and the perforating groove ring. The perforating blade and groove ring can also be adjusted, so that alignment requires matching the adjustment or adjusted position of the second longitudinal folding apparatus with respect to the adjusted position of the perforating blade and its associated perforating groove ring.